The xml itself can/will contain different grammars depending upon the payload (config, build, content, rules, etc). So, when someone interviews for a position, it is nice to give them a lot of code (say an eclipse/netbeans/idea project) and ask them to add a new feature to the code.

It’s important to let the interviewee(candidate) do this for all the artifacts that they are expected to create/USE(java/xml, SQL etc). It’s also good to have some sample code available for them so that they can do copy/paste. This is so that the candidate does not fail just on syntax.

If, as Joel says, it takes smarts + “getting things done” attitude to succeed at his company, the above exercise should take care of “GETTING THINGS DONE”. I guess the puzzles and related questions go a long way at testing a person’s smarts ?